This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. We created three knock-in mice in which the mouse avpr1a promoter was replaced by the prairie vole avpr1a promoter. The three mouse lines differ only in the microsatellite element in the promoter that we believe may be contributing to both species and individual differences in avpr1a expression, as well as variation in social behavior. Three different constructs contain either a meadow vole, long prairie vole, or short prairie vole microsatellite. We continued to make progress in our prairie vole selective breeding scheme in which we selected prairie vole lines that differ in their ability to form social bonds. We have completed 4 generations of selection. After just 3 generations we are achieving separation in our lines. Once we have achieved significant differences in behavior for 2 consecutive generations, we will examine brain vasopressin receptor differences. We continue making processes collecting DNA samples from our collaborators Drs Skuse and Puura. We collected DNA samples and social cognition test scores from 420 individuals. The sample collection is going as planned. We do not expect to conduct the genetic analysis of these samples until year 4 or the beginning of year 5. In order to better understand vasopressin receptors role in pair bond formation, we conducted an experiment in which we blocked vasopressin receptors either prior to or after cohabitation with a female, but prior to partner preference testing. Results show that vasopressin receptor activation is necessary both for the formation and expression of partner preference, but not for consolidation of the memory.